I'm not aware of fx loop boosting devices. This is a quite unusual thing as it would be very easy to ruin the amp (and gtr) tone if not done properly. The best solution would be using a more adequate amp for low power use. Unfortunately there are some technical aspects we need to consider when using electronic gear.
One thing that many use and that seems to make everything_speak_to_everything_else quite well is the Soundsculpture Switchblade. It's a bit expensive but does a lot. You may enjoy reading its documentation and talk to them for advice on the topic.